ISO/TS 10303-28:2003 specifies use of the Extensible Markup Language (XML) to represent schemas specified using the EXPRESS data specification language, ISO 10303-11, and data that is governed by EXPRESS schemas.

The following are within the scope of ISO/TS 10303-28:2003:

• specification of XML markup declarations that enable EXPRESS schemas to be represented using XML;
• specification of a single XML markup declaration set that is independent of the EXPRESS schema and formally describes the XML representation of data governed by any schema;

NOTE 1 XML markup declarations specified using this method are referred to as late bound, in that they may be used without change to represent data governed by any EXPRESS schema. ISO/TS 10303-28:2003 allows for a number of choices in representing the data.

• for an arbitrary EXPRESS schema, specification of an XML markup declaration set that corresponds to the schema and formally describes the XML representation of data governed by that schema;

NOTE 2 XML markup declarations specified using these methods are referred to as early bound, in that they are specific to a given EXPRESS schema.

• specification of the mapping between XML markup declarations corresponding to a specific schema and the XML markup declarations independent of any schema;
• specification of the form of XML documents containing EXPRESS schemas and data governed by EXPRESS schemas;
• specification of the representation of EXPRESS primitive data type values as element content and as XML attribute values.

The following are outside the scope of ISO/TS 10303-28:2003:

• specification of XML markup declarations corresponding to an EXPRESS schema that depend on the semantic intent of the EXPRESS schema;
• specification of mappings from XML markup declarations to an EXPRESS schema;

NOTE 3 Given a set of XML markup declarations and one or more corresponding data sets, it is feasible to create an EXPRESS schema that captures the semantic intent of the data. However, this requires an understanding of the meaning and use of the data that may not be captured by the XML markup declarations.

• specification of the mapping to an EXPRESS schema from an XML representation of that schema;
• specification of the mapping to an EXPRESS schema from XML markup declarations that have been derived from that schema;
• any mapping to or use of XML schema.